The present invention relates to an apparatus for and a method of recording data on and reproducing data from an optical disk having concentric or spiral recording tracks formed of grooves and lands between the grooves, with the land and groove tracks being divided into sectors, and with address areas for the respective sectors being disposed between the center of a groove and the center of a land adjacent to each other, so that during reproduction of a track, an address for a sector in the track and an address for a sector in an adjacent track are both reproduced.
In a typical example, the address areas for the respective tracks are shifted in one radial direction (e.g., radially outwards), and during reproduction of the track, the address for a sector in the track and the address for a sector in another track adjacent to and disposed in the other radial direction (e.g., radially inward) of the first-mentioned track are both reproduced.
As a data recording method for a large-capacity rewritable optical disk, with an increased recording density, a land/groove recording method has been proposed in which data is recorded both onto the grooves of guide grooves (also referred to G), and onto lands (also referred to L) between the grooves. When this method is used, the recording density can be increased because the track pitch can be halved compared to an optical disk which has the same groove pitch but does not use this method. Grooves and lands may also be referred to as depressed portions and projecting portions, respectively.
An example of conventional land/groove recording optical disk, disclosed in Japanese Examined Patent Application Publication 63-57859 is shown in FIG. 11. As illustrated, grooves 94 and lands 95 are formed by means of guide grooves inscribed on the substrate of the disk, and a recording layer 91 is formed thereon. Recording pits 92 are formed on the recording layer 91 on the grooves 94 and the lands 95. The grooves 94 and the lands 95 form separate continuous recording tracks. That is, the guide grooves are continuous on the disk, so that the recording tracks of the grooves 94 form a continuous recording spiral, and the recording tracks of the lands 95 form a separate continuous recording spiral. A light spot 93 generated by an optical disk drive apparatus records data on or reproduces data from the optical disk, while scanning either of the recording tracks of the lands and the grooves.
In another format, which is shown in FIG. 12, lands and grooves are connected at every revolution to form a single spiral in which lands L and grooves G alternate at very revolution. More specifically, a recording track of a groove (hereinafter referred to as a groove track) having a length corresponding to a revolution of the disk and a recording track of a land (hereinafter referred to as a land track) having a length corresponding to a revolution of the disk are connected alternately to form a recording spiral. This format is herein referred to as a single spiral land/groove format, or an SS-L/G format.
The recording surface of the optical disk is divided into a plurality of annular zones (Z1, Z2), and each revolution of the track is divided into an integer number of sectors RS having an identification data area IDF. The number of sectors per track is progressively increased by "one" toward the outermost zone. In the example shown in FIG. 12, the disk is divided into two zones (Z1, Z2), and the number of sectors per track is three in the inner zone Z1, and is four in the outer zone Z4.
FIG. 13 schematically shows the arrangement of identification data area IDF and the address values recorded within a recording sector RS of an optical disk used with a conventional optical disk drive apparatus. n represents an address of a certain sector, and N represents the number of sectors per track. The identification data area IDF is composed of four PIDs (Physical IDs) and divided into a front part FP and a rear part RP in the beam spot scanning direction SCN. Each of the front part FP and the rear part RP is composed of two PIDs. The front part FP is shifted radially outwards (OP) by half a groove width Dw/2 from the center of a groove, while the rear part RP is shifted radially inwards (IP) by half the groove width from the center of the groove.
A method of providing identification data such as a sector address in the identification data area IDF is described next. The address of a groove track sector is assigned to the front part FP of the identification data area IDF which is immediately before the data recording area DRF of the groove track sector, being shifted by half a groove width radially outwards from the center of the groove. On the other hand, the address of a land track sector is assigned to a rear part RP of the identification data area IDF which is immediately before the data recording area DRF in a groove track sector adjacent to and disposed radially outward of the above-mentioned land track sector, being shifted radially inwards by half the groove width from the center of the groove. Consequently, the address of a land track sector is assigned to the rear part RP of the identification data area IDF in a groove track sector, which is immediately before the data recording area DRF of the land track sector, and which is shifted radially outwards by half a groove width from the center of the land. In this way, the address of a land track sector is added to a groove rather than to a land, and an identification data area IDF in a land track sector contains no identification data.
An advantage of having the identification data shifted by half a groove width from the center of a track is that the identification data are shared between a groove track and a land track adjacent to each other, so that the identification data are read with a substantially the same quality, regardless of whether a track sector being scanned is in a land or a groove. When the width of a groove is not identical to a track pitch, the amount of the shift may be set to half a track pitch.
For simplifying the description, it is assumed in FIG. 13 that an identification data area IDF is composed of four PIDs alone. The identification data area IDF may further contain other information such as a header mark or servo control data. Also, synchronization data for address reading, and error detection or error correction codes may also be provided as is known in the art.
Now, description is directed to the prepits in identification data areas around a land/groove connecting points, which are present at every revolution of a disk and which are aligned in a radial direction of the disk, and a method of assigning addresses to such identification data areas. FIG. 14 schematically shows the arrangement of identification data areas within the sectors around connecting points or boundaries between lands and grooves, and the address values assigned thereto. In an SS-L/G format optical disk, there is a boundary extending in the radial direction, at which a land track and a groove track are connected at every revolution of the disk. In a recording sector RS immediately after a land/groove connecting point, the front part FP of the identification data is shifted by half a groove width radially outwards from the center of the groove, and the rear part RP of the identification data area IDF is shifted by half a groove radially inwards from the center of the groove, as in the identification data areas IDF in other sectors (sectors which are not at the connecting points). The assignment of the addresses is also the same as in the sectors which are not at the connecting points. That is, the address of a groove track sector is assigned to the front part FP of the identification data area IDF which is immediately before the data recording area DRF and which is shifted radially outwards by half a groove width from the groove. The address of a land track sector is assigned to the rear part RP of the identification data area IDF which is immediately before the data recording area DRF and which is shifted by half a groove width radially outwards from the land.
In order to detect a land/groove connecting point, determination is made in which radial direction the front part FP of the identification data area IDF and the rear part RP of the identification data area IDF are shifted with respect to the center of a track in a state in which tracking is achieved. The address of a groove track sector can be identified as the address data read from the front part FP of the identification data area IDF, which is shifted radially outwards by half a groove width from the groove, while the address of a land track sector can be identified as the address data read from the rear part RP of the identification data area IDF which is shifted radially outwards by half a groove width from the land. In either case, the part which is shifted radially outwards represents the address of the sector, while the part which is shifted radially inwards represents the address of a sector disposed radially inward of and adjacent to the the sector.
When an optical disk drive apparatus for recording data on and reproducing data from an optical disk having the above track configuration detects sector addresses, it obtains the address values in the following manner. That is, when a groove is being scanned, the address value of the PIDs from the front part FP of the identification data area IDF which is shifted radially outwards is read. On the other hand, when a land is being scanned, the address value of the PIDs from the rear part RP of the identification data area IDF which is shifted radially inwards is read.
Because the conventional optical disk drive apparatus performs detection of sector addresses in the above-described manner, it can read four PID data by scanning an identification data area IDF. The address recognition, however, is performed by using the two specific PID data out of the four PID data, depending on whether the sector being scanned is in a groove or land. That is, although four addresses are contained in an identification data area IDF, only the two addresses are used for the address recognition. Thus, the ratio of correct address identification is limited.
When it was attempted to use all of the four addresses recorded in the PIDs, it was necessary to provide a memory for storing the number N of sectors per track in the zone being scanned. All of the four addresses can be utilized only because the difference between the address value of a groove track sector and the address value of a land track sector adjacent thereto is always N. If the address of a groove track sector and the address of a land track sector adjacent thereto are independent of each other, all of the four addresses cannot be utilized.
Further, whether the track being scanned is in a groove or a land should be recognized in order to determine whether the front part FP or the rear part RP of an identification data area IDF should be read. If the determination fails for any reason, the identification of the address cannot be achieved.